Circuits and methods related to power detectors for radio-frequency applications

ABSTRACT

Circuits and methods related to power detectors for radio-frequency (RF) applications. In some embodiments, a power amplifier (PA) system can include a PA circuit having a driver stage and an output stage. The PA system can further include a detector configured to receive a portion of an RF signal from a path between the driver stage and the output stage. The detector can be further configured to generate an output signal representative of power associated with the RF signal and compensated for variation in at least one operating condition associated with the PA circuit.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. Provisional Application No.62/003,072 filed May 27, 2014, entitled CIRCUITS AND METHODS RELATED TOPOWER DETECTORS FOR RADIO-FREQUENCY APPLICATIONS, the disclosure ofwhich is hereby expressly incorporated by reference herein in itsentirety.

BACKGROUND

1. Field

The present disclosure relates to power detectors for radio-frequency(RF) applications.

2. Description of the Related Art

In many radio-frequency (RF) applications an RF signal to be transmittedcan be amplified by a power amplifier (PA). Such a PA can include aplurality of stages, such as a driver stage and an output stage. Theamplified RF signal output by the PA can be transmitted through anantenna.

SUMMARY

According to a number of implementations, the present disclosure relatesto a power amplifier (PA) system that includes a PA circuit having adriver stage and an output stage. The PA system further includes adetector configured to receive a portion of a radio-frequency (RF)signal from a path between the driver stage and the output stage. Thedetector is further configured to generate an output signalrepresentative of power associated with the RF signal and compensatedfor variation in at least one operating condition associated with the PAcircuit.

In some embodiments, the RF signal can be an output of the driver stage.The PA system can further include a control circuit configured toreceive the output signal of the detector and adjust a transmitoperation. The transmit operation can be performed by a transmittercircuit which can be part of a transceiver.

In some embodiments, the detector can include a detecting circuitconfigured to receive the portion of the RF signal and generate aslow-varying or DC voltage Vin representative of the power associatedwith the RF signal. The detector can further include a compensationcircuit configured to receive Vin and generate a compensation signalrepresentative of the variation in at least one operating conditionassociated with the PA circuit. The compensation signal can include acompensation current Iout resulting from a combination of a current Iinrepresentative of Vin and an operating condition current representativeof the at least one operating condition. The current Iin and theoperating condition current can be combined by a current multiplier.

In some embodiments, the at least one operating condition can include aPA temperature and a supply voltage. In some embodiments, the detectorcan further include an output circuit configured to receive Vin andIout, and generate an output signal having the compensation associatedwith Iout applied to Vin. The output signal can be an output voltageVout. The output circuit can be configured such that Vout adds a voltagerepresentative of Iout to Vin.

In some teachings, the present disclosure relates to a method foroperating a power amplifier (PA) system. The method includes amplifyinga radio-frequency (RF) signal with a PA circuit that includes a driverstage and an output stage. The method further includes obtaining aportion of the RF signal from a path between the driver stage and theoutput stage. The method further includes generating an output signalrepresentative of power associated with the RF signal and compensatedfor variation in at least one operating condition associated with the PAcircuit. In some embodiments, the at least one operating condition caninclude either or both of a PA temperature and a supply voltage.

In some implementations, the present disclosure relates to aradio-frequency (RF) module that includes a packaging substrateconfigured to receive a plurality of components, and a power amplifier(PA) system implemented on the packaging substrate. The PA systemincludes a PA circuit having a driver stage and an output stage. The PAsystem further includes a detector configured to receive a portion of aradio-frequency (RF) signal from a path between the driver stage and theoutput stage. The detector is further configured to generate an outputsignal representative of power associated with the RF signal andcompensated for variation in at least one operating condition associatedwith the PA circuit.

In some embodiments, the PA circuit can be implemented on a first die,and the detector can be implemented on a second die. In someembodiments, at least some of the PA circuit and at least some of thedetector can be implemented on a common die. In some embodiments,substantially all of the PA circuit and substantially all of thedetector can be implemented on the common die. In some embodiments, thePA system can be configured to amplify an RF signal for a wireless localarea network (WLAN).

In accordance with a number of implementations, the present disclosurerelates to a wireless device that includes a transmitter circuitconfigured to generate a radio-frequency (RF) signal, and a poweramplifier (PA) system in communication with the transmitter circuit. ThePA system includes a PA circuit having a driver stage and an outputstage, and a detector configured to receive a portion of aradio-frequency (RF) signal from a path between the driver stage and theoutput stage. The detector is further configured to generate an outputsignal representative of power associated with the RF signal andcompensated for variation in at least one operating condition associatedwith the PA circuit. The wireless device further includes an antenna incommunication with the PA system, with the antenna being configured totransmit the RF signal. In some embodiments, the antenna can be awireless local area network (WLAN) antenna.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts a radio-frequency (RF) system having adetector implemented to detect power along an RF amplification pathbetween a driver stage and an output stage.

FIG. 2 shows an example of a control system that can be implemented witha detector that measures power associated with a partially amplified RFsignal.

FIG. 3 shows an example configuration of a detector that can beimplemented as the detector of FIGS. 1 and 2.

FIG. 4 shows an example of a detector that can be a more specificexample of the detector of FIG. 3.

FIG. 5 shows examples of how the compensated Vout in FIG. 4 can havereduced sensitivity to variations in PA temperature and supply voltage.

FIG. 6 shows an example of a packaged module where a detector having oneor more features as described herein can be implemented on a die that isseparate from a die having a PA.

FIG. 7 shows an example of a packaged module where a detector having oneor more features as described herein can be implemented on a die thatalso includes a PA.

FIG. 8 depicts an example wireless device having one or moreadvantageous features described herein.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

In many radio-frequency (RF) applications, it is desirable to measurepower levels of power amplifiers (PAs). For example, an integrated powerdetector can be incorporated into a wireless local area network (WLAN)PA to allow a power output level to be set accurately. To provide gooddirectivity, a detector can either utilize a directional coupler on anoutput stage of a PA, or be implemented to detect a signal at a driverstage of the PA.

Couplers are typically large and can result in loss of some PA power.Accordingly, such couplers are not desirable in some PA applications. Inthe context of detection at the driver stage, a power detector istypically sensitive to variations in the gain of the output stage whichcan occur with, for example, variations in supply voltage and/ortemperature.

Disclosed herein are circuits, devices and method related to detectionof power at an output of a driver stage of a PA. For the purpose ofdescription, it will be understood that such an output of the driverstage can be between the first and last stages in an amplification pathwith two or more stages. It will also be understood that detection ofpower as described herein can be implemented on a partially amplified RFsignal. Although described in such an example context, it will beunderstood that one or more features of the present disclosure can alsobe implemented in other portions of an amplification path of a PA. Forthe purpose of description, it will be understood that detection ofpower can include detection of current, voltage, or some combinationthereof, associated with RF signals.

FIG. 1 schematically depicts an RF system 100 having a detector 114implemented to detect power along an RF amplification path between adriver stage 104 and an output stage 106 of a PA 116. The PA 116 isshown to receive an RF signal to be transmitted from a transceiver 102.The amplified RF signal from the PA 116 can be routed to an antenna 110through, for example, an antenna switching module (ASM) 108. In someembodiments, such an amplification configuration can be implemented in,for example, a wireless local area network (WLAN) PA system and/or otherPA systems.

FIG. 1 further shows that in some embodiments, the detector 114 can becoupled to the transceiver 102. As described herein in greater detail, acontrol circuit in the transceiver 102 can receive an output signalrepresentative of the detected power from the detector 114. Based onsuch an output signal, the RF signal generated by the transceiver 102can be adjusted appropriately.

FIG. 2 shows an example of a control system 120 that can be implementedwith a detector 114 that measures power associated with a partiallyamplified RF signal. For example, an RF signal generated by atransceiver 102 can be provided to a driver stage 104 of a PA 116through path 122. A path 124 can be provided between the driver stage104 and an output stage 106 to route the partially amplified RF signalfrom the driver stage 104 to the output stage 106. The output stage 106is shown to yield an amplified RF signal through path 126.

As shown in FIG. 2, the detector 114 can measure the power levelassociated with the partially amplified RF signal through node 128 alongthe path 124. As further shown in FIG. 2, the detector 114 can generateand provide a detector signal to a control component 134 that is coupledthrough, for example, path 130 and node 132. In the example of FIG. 2,the control component 134 is depicted as being part of the transceiver102; however, it will be understood that some or all of the controlcomponent 134 can be implemented at other locations.

FIG. 3 shows an example configuration of a detector 114 that can beimplemented as the detector of FIGS. 1 and 2. In the example of FIG. 3,an input to the detector 114 can be representative of power associatedwith an RF signal, and such an input can be provided through an RF input(RFin) node 128. Such a node can be, for example, node 128 in FIG. 2. Anoutput signal generated by the detector 114 can be provided as, forexample, an output voltage (Vout) at node 132. Such a node can be, forexample, node 132 in FIG. 2.

FIG. 3 shows that in some embodiments, the detector 114 can include adetecting circuit 140 configured to receive an input signal sampled froma partially amplified RF signal (e.g., an output of the driver stage).As described herein, the detecting circuit 140 can be configured toreceive the input signal and generate a voltage Vin having a magnituderepresentative of the magnitude of the partially amplified RF signal.

The voltage Vin is shown to be provided to an output circuit 146, aswell as to a compensation circuit 141. The compensation circuit 141 isshown to generate a compensation current Icomp based on Vin and one ormore currents that correspond to operating condition(s). Thecompensation current Icomp is shown to be combined with Vin to yield anoutput voltage Vout that represents the power associated with thepartially amplified RF signal, compensated for the one or more operatingconditions.

In FIG. 3, the example operating conditions are depicted as temperatureof the PA (e.g., PA die temperature) and supply voltage provided to thePA. A current generator 143 can be configured to generate Itemp which isa current representative of the PA temperature; and a current generator144 can be configured to generate Isupply which is a currentrepresentative of the supply voltage. A current generator 142 can beconfigured to generate Iin which is a current representative of theinput voltage Vin.

In some embodiments, the compensation circuit 141 can include a combiner145 configured to combine Itemp, Isupply, and Iin to generate thecompensation current Icomp. Examples of the current generators 142, 143,144 are described herein in greater detail.

FIG. 4 shows an example of a detector 114 that can be a more specificexample of the detector 114 described in reference to FIG. 3. Asdescribed herein, the input to the detector 114 can be representative ofthe power associated with an output of the driver stage. In someembodiments, such an in input can be processed with a diode detectiontechnique. For example, a diode D1 (e.g., a Schottky diode) can receivea sampled RF signal representative of the partially amplified RF signalat the output of the driver stage, and yield a slow-varying or DCcurrent or voltage having a magnitude that is approximately proportionalto the magnitude of the sampled RF signal. To achieve suchproportionality, the rectified signal at node 150 can charge acapacitance (e.g., a capacitor) C1 to a voltage that is approximatelyproportional to the sampled RF signal amplitude.

The capacitance C1 is shown to couple node 150 to a signal ground. Acurrent source 11 implemented between node 150 and the signal groundallows a discharge path for the capacitor C1 so that the voltage on node150 follows the modulation of the RF envelope with most of the RFcarrier signal removed. This voltage on node 150 can be passed through alow pass filter 154 (e.g., a 2 MHz low pass filter) to remove or reducehigher frequency components of the modulation to yield an input voltageVin at node 156. The low pass filter 154 can include, for example, an RFfilter in which a resistance R1 is provided between nodes 150 and 156,and a capacitance C1 couples node 156 to the signal ground.

The input voltage Vin resulting from the foregoing diode detectorcircuit and the low pass filter can be sensitive to variations in thegain of the output stage which can occur when the PA supply voltageand/or the PA temperature are changed. Thus, Vin can be compensated forone or more of such operating conditions. Although described in thecontext of PA supply voltage and PA temperature, it will be understoodthat compensation can be based on other operating and/or environmentalconditions.

In the example of FIG. 4, compensation for the PA supply voltagevariation and the PA temperature variation can be achieved in terms ofcurrents representative of such variations. For example, a currentgenerator 12 can receive a supply voltage Vcc from node 174 and generatea current that corresponds to a change in PA temperature. In someembodiments, the current generator 12 can be configured so that itsoutput current increases when the PA temperature increases. Such anoutput current can be generated based on, for example, currentproportional to absolute temperature.

In another example, a current generator 13 can receive the supplyvoltage Vcc from node 174 and generate a current that corresponds to achange in the supply voltage itself. For example, the current generator13 can be configured so that its output current is proportional to thesupply voltage. In some embodiments, such a current generator can beconfigured and operated in a known manner.

As shown in FIG. 4, an op amp 170 combined with first field-effecttransistor (FET) M1 (e.g., PFET) and a resistor R3 can cause a currentto flow in R3 so that the voltages on the input terminals of the op amp170 are matched. Thus, in such a configuration, the current in M1 isproportional to Vin. This current in M1 is shown to be mirrored by M2 toproduce a current I_(A) at node 175.

In some embodiments, the current sources 12 and 13 may be used ascontrol elements for a current multiplier 180. As described herein, thecurrent multiplier 180 modifies the current I_(A) using currents I_(B)and I_(C) from their respective sources 12 and 13 to compensate for PAtemperature and supply voltage variations.

In the example of FIG. 4, the currents I_(A), I_(B) and I_(C) generallycorrespond to the currents I_(in), I_(temp) and I_(supply),respectively, as described in reference to FIG. 3. In such a context,I_(A), I_(B) and I_(C) are shown to be provided to the currentmultiplier 180 through their respective nodes 175, 176, 177. In someembodiments, the current multiplier 180 can be configured to generate anoutput of AB/C. Accordingly, an output current from the currentmultiplier 180 can be represented asIout=I_(A)I_(B)/I_(C)=(Vin/R3)I_(B)/I_(C).

It will be understood that the foregoing multiplier functionality ofAB/C is an example, and that other functions can be implemented by thecurrent multiplier 180. Accordingly, the output current can berepresented in a more general form as Iout=(Vin/R3)×f(Vbat, temp), wheref(Vbat, temp) is a function of Vbat and temperature.

In FIG. 4, such an output current Iout from the current multiplier 180is shown to be provided to an inverting input of an op amp 160. Vin fromnode 156 is shown to be provided to a non-inverting input of the op amp160. An output Vout of the op amp 160 is shown to be provided to anoutput node 132, as well as to the inverting input through a resistanceR2 to form a negative feedback loop. Such a configuration can result inthe output voltage Vout to be Vin plus Iout scaled by the feedback loopresistance R2. Accordingly, Vout can be expressed asVout=Vin+(Iout)(R2). Since Iout=(Vin/R3)×f(Vbat, temp), Vout can beexpressed as Vout=Vin[1+(R2/R3) f(Vbat, temp)].

It is noted that in some embodiments, all of the detector signal (e.g.,at node 156) can be put through the compensation loop and not use thepositive terminal of the op amp 160. However, such a configuration maybe subjected to offset problems that can affect current multipliercircuits for variations in Vin that may not be too large. For example,voltage Vin can vary in the order of about 20% for temperature changesof −40 degree to +120 degree and supply voltage changes of 3V to 5V.

In the example of FIG. 4, Vout reflects compensation of the measuredpower associated with the input RF signal (RFin). As described herein,such a compensation can include either or both of PA temperature andsupply voltage. It will be understood that compensation can also beperformed for other operating conditions.

FIG. 5 shows examples of how the compensated Vout in FIG. 4 can havereduced sensitivity to PA temperature and supply voltage. In FIG. 5,various Vout curves are plotted as a function of PA temperature. Curves200, 202, 204 are for Vout without compensation, and curves 210, 212,214 are for Vout with compensation. For the uncompensated curves 200,202, 204, Vout can be Vin (e.g., at node 156 in FIG. 4). For thecompensated curves 210, 212, 214, Vout can be obtained from the outputnode 132 in FIG. 4.

In FIG. 5, the curve 200 is obtained at a supply voltage of 3.0V; thecurve 202 is obtained at a supply voltage of 3.3V; and the curve 204 isobtained at a supply voltage of 3.6V. The curve 210 is obtained at asupply voltage of 3.6V; the curve 212 is obtained at a supply voltage of3.3V; and the curve 214 is obtained at a supply voltage of 3.0V. Fromthe two groups of curves (200, 202, 204 in the uncompensatedconfiguration, and 210, 212, 214 in the compensated configuration), onecan see that the uncompensated detector output has a significantdependence on the PA temperature, while the compensated detector outputis essentially insensitive to PA temperature variation. One can also seethat for the uncompensated configuration, variation in the supplyvoltage results in noticeable shifts of the detector output. For thecompensated configuration, the detector output is again essentiallyinsensitive to supply voltage variation.

In some embodiments, at least a portion of a detector having one or morefeatures as described herein (e.g., 114 in FIGS. 1-4) can be implementedon a semiconductor die. Such a semiconductor die may or may not be thesame die on which the PA (e.g., 116 in FIGS. 1 and 2) is implemented.For example, both of the detector 114 and the PA 116 can be implementedon a BiCMOS die. In another example, if the PA 116 is implemented on aGaAs die, it may not be desirable or practical to implement the detector114 on the same die. Accordingly, the detector 114 can be implemented ona die that is different from the PA die.

FIG. 6 shows an example of a packaged module 300 where a detector 114having one or more features as described herein can be implemented on adie 360 that is separate from a die 302 having a PA 116. In the exampleof FIG. 6, both of the die 360, 302 are shown to be mounted on apackaging substrate 350 that is configured to receive a plurality ofcomponents. Such components can include one or more die, such as theexample die 360, 302, as well as one or more surface mounted devices(SMDs) such as passive components. In some embodiments, the packagingsubstrate 350 can include, for example, a laminate substrate.

In the example of FIG. 6, the die 360 can include a plurality ofelectrical contact pads 362 configured to allow formation of electricalconnections 364 such as wirebonds between the die 360 and contact pads366 formed on the packaging substrate 350. Similarly, the die 302 caninclude a plurality of electrical contact pads 352 configured to allowformation of electrical connections 354 such as wirebonds between thedie 302 and contact pads 356 formed on the packaging substrate 350.

FIG. 7 shows an example of a packaged module 300 where a detector 114having one or more features as described herein can be implemented on adie 370 that also includes a PA 116. In the example of FIG. 7, the die370 is shown to be mounted on a packaging substrate 350 that isconfigured to receive a plurality of components. Such components caninclude one or more die, such as the example die 370, as well as one ormore surface mounted devices (SMDs) such as passive components. In someembodiments, the packaging substrate 350 can include a laminatesubstrate. In the example of FIG. 7, the die 370 can include a pluralityof electrical contact pads 352 configured to allow formation ofelectrical connections 354 such as wirebonds between the die 370 andcontact pads 356 formed on the packaging substrate 350.

In some embodiments, each of the modules 300 of FIGS. 6 and 7 can alsoinclude one or more packaging structures to, for example, provideprotection and facilitate easier handling of the module 300. Such apackaging structure can include an overmold formed over the packagingsubstrate 350 and dimensioned to substantially encapsulate the variouscircuits and components implemented on the packaging substrate. It willbe understood that although the module 300 is described in the contextof wirebond-based electrical connections, one or more features of thepresent disclosure can also be implemented in other packagingconfigurations, including flip-chip configurations.

In some embodiments, a die having the PA 116 with its detector 114 canimplemented in a packaging configuration that does not necessarily relyon a laminate substrate. For example, such a die can be implementeddirectly in a QFN type package and not rely on a laminate.

It will also be understood that although the examples of FIGS. 6 and 7are described in the context of wirebond die, one or more features ofthe present disclosure can be implemented in other types of die. Forexample, a flip chip PA die can include some or all of a detector 114 asdescribed herein.

In some implementations, a device and/or a circuit having one or morefeatures described herein can be included in an RF device such as awireless device. Such a device and/or a circuit can be implementeddirectly in the wireless device, in a modular form as described herein,or in some combination thereof. In some embodiments, such a wirelessdevice can include, for example, a base station configured to providewireless services, a cellular phone, a smart-phone, a hand-held wirelessdevice with or without phone functionality, a wireless tablet, etc.

FIG. 8 schematically depicts an example wireless device 400 having oneor more advantageous features described herein. In the context ofvarious configurations described herein, one or more modules havingfunctionality depicted as 300 can be included in the wireless device400. As described herein, such a module can include functionalityassociated with a detector 114 having one or more features as describedherein, and functionality associated with a PA 116.

For example, a front-end module (FEM) 300 for WLAN/GPS operations caninclude a PA 116 and a detector 114 having one or more features asdescribed herein. Such a PA can be configured to amplify a WLAN signalfor transmission through an antenna 456. Such a WLAN signal can begenerated by a baseband sub-system 408 and routed to the FEM 300 througha WLAN/Bluetooth system-on-chip (SOC) 460.

In the example of FIG. 8, transmission and reception of Bluetoothsignals can be facilitated by an antenna 458. In the example shown, GPSfunctionality can be facilitated by the FEM 300 in communication with aGPS antenna 454 and a GPS receiver 450.

In another example, an RF PA module depicted as 300 can include one ormore features as described herein. Such an RF PA module 300 can includeone or more bands, and each band can include one or more amplificationstages. One or more of such amplification stages can be in communicationwith one or more detectors (114) and benefit from the compensated powerdetection techniques as described herein.

In the example wireless device 400, the RF PA module 300 having aplurality of PAs can provide an amplified RF signal to a switch 414 (viaduplexer 412), and the switch 414 can route the amplified RF signal toan antenna 416. The PA module 300 can receive an unamplified RF signalfrom a transceiver 410.

The transceiver 410 can also be configured to process received signals.Such received signals can be routed to an LNA (not shown) from theantenna 416, through the duplexer 412. As described herein, thetransceiver 410 can also include a controller (e.g., 134 in FIG. 2)configured to receive the detected power signal and operate thetransceiver 410 accordingly.

The transceiver 410 is shown to interact with a baseband sub-system 408that is configured to provide conversion between data and/or voicesignals suitable for a user and RF signals suitable for the transceiver410. The transceiver 410 is also shown to be connected to a powermanagement component 406 that is configured to manage power for theoperation of the wireless device 400. Such a power management componentcan also control operations of the baseband sub-system 408, as well asother components.

The baseband sub-system 408 is shown to be connected to a user interface402 to facilitate various input and output of voice and/or data providedto and received from the user. The baseband sub-system 408 can also beconnected to a memory 404 that is configured to store data and/orinstructions to facilitate the operation of the wireless device, and/orto provide storage of information for the user.

A number of other wireless device configurations can utilize one or morefeatures described herein. For example, a wireless device does not needto be a multi-band device. In another example, a wireless device caninclude additional antennas such as diversity antenna, and additionalconnectivity features such as Wi-Fi, Bluetooth, and GPS.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Description using the singularor plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While some embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A power amplifier (PA) system comprising: a PAcircuit including a driver stage and an output stage; and a detectorconfigured to receive a portion of a radio-frequency (RF) signal from apath between the driver stage and the output stage, the detector furtherconfigured to generate an output signal representative of powerassociated with the RF signal and compensated for variation in at leastone operating condition associated with the PA circuit.
 2. The PA systemof claim 1 wherein the RF signal is an output of the driver stage. 3.The PA system of claim 1 further comprising a control circuit configuredto receive the output signal of the detector and adjust a transmitoperation.
 4. The PA system of claim 3 wherein the transmit operation isperformed by a transmitter circuit.
 5. The PA system of claim 4 whereinthe transmitter circuit is part of a transceiver.
 6. The PA system ofclaim 1 wherein the detector includes a detecting circuit configured toreceive the portion of the RF signal and generate a slow-varying or DCvoltage Vin representative of the power associated with the RF signal.7. The PA system of claim 6 wherein the detector further includes acompensation circuit configured to receive Vin and generate acompensation signal representative of the variation in at least oneoperating condition associated with the PA circuit.
 8. The PA system ofclaim 7 wherein the compensation signal includes a compensation currentIout resulting from a combination of a current Iin representative of Vinand an operating condition current representative of the at least oneoperating condition.
 9. The PA system of claim 8 wherein the current Iinand the operating condition current are combined by a currentmultiplier.
 10. The PA system of claim 8 wherein the at least oneoperating condition includes a PA temperature and a supply voltage. 11.The PA system of claim 8 wherein the detector further includes an outputcircuit configured to receive Vin and Iout, the output circuit furtherconfigured to generate an output signal having the compensationassociated with Iout applied to Vin.
 12. The PA system of claim 11wherein the output signal is an output voltage Vout.
 13. The PA systemof claim 12 wherein the output circuit is configured such that Vout addsa voltage representative of Iout to Vin.
 14. A method for operating apower amplifier (PA) system, the method comprising: amplifying aradio-frequency (RF) signal with a PA circuit, the PA circuit includinga driver stage and an output stage; obtaining a portion of the RF signalfrom a path between the driver stage and the output stage; andgenerating an output signal representative of power associated with theRF signal and compensated for variation in at least one operatingcondition associated with the PA circuit.
 15. The method of claim 14wherein the at least one operating condition includes either or both ofa PA temperature and a supply voltage.
 16. A radio-frequency (RF) modulecomprising: a packaging substrate configured to receive a plurality ofcomponents; and a power amplifier (PA) system implemented on thepackaging substrate, the PA system including a PA circuit having adriver stage and an output stage, the PA system further including adetector configured to receive a portion of a radio-frequency (RF)signal from a path between the driver stage and the output stage, thedetector further configured to generate an output signal representativeof power associated with the RF signal and compensated for variation inat least one operating condition associated with the PA circuit.
 17. TheRF module of claim 16 wherein the PA circuit is implemented on a firstdie, and the detector is implemented on a second die.
 18. The RF moduleof claim 16 wherein at least some of the PA circuit and at least some ofthe detector are implemented on a common die.
 19. The RF module of claim18 wherein substantially all of the PA circuit and substantially all ofthe detector are implemented on the common die.
 20. The RF module ofclaim 16 wherein the PA system is configured to amplify an RF signal fora wireless local area network (WLAN).